[Macros] Type-check macro-generated extensions via the top-level decls of

the synthesized source file instead of a separate API to gather the
extensions.

This is how macro-generated extensions are visited everywhere else.

(cherry picked from commit 3ecfb53)

Author: hborla

include/swift/AST/Decl.h

@@ -924,12 +924,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
       bool visitFreestandingExpanded = true
   ) const;
 
-  using ExtensionCallback = llvm::function_ref<void(ExtensionDecl *)>;
-
-  /// Iterate over each macro-expanded extension for this declaration,
-  /// invoking the given callback with each extension.
-  void forEachExpandedExtension(ExtensionCallback callback) const;
-
   using MacroCallback = llvm::function_ref<void(CustomAttr *, MacroDecl *)>;
 
   /// Iterate over each attached macro with the given role, invoking the

lib/AST/Decl.cpp

@@ -422,29 +422,6 @@ void Decl::visitAuxiliaryDecls(
   // FIXME: fold VarDecl::visitAuxiliaryDecls into this.
 }
 
-void
-Decl::forEachExpandedExtension(ExtensionCallback callback) const {
-  auto &ctx = getASTContext();
-  auto *mutableThis = const_cast<Decl *>(this);
-  auto *nominal = dyn_cast<NominalTypeDecl>(mutableThis);
-  if (!nominal)
-    return;
-
-  SourceManager &sourceMgr = ctx.SourceMgr;
-  auto *moduleDecl = getModuleContext();
-  auto conformanceBuffers =
-      evaluateOrDefault(ctx.evaluator,
-                        ExpandConformanceMacros{nominal},
-                        {});
-  for (auto bufferID : conformanceBuffers) {
-    auto startLoc = sourceMgr.getLocForBufferStart(bufferID);
-    auto *sourceFile = moduleDecl->getSourceFileContainingLocation(startLoc);
-    for (auto *extension : sourceFile->getTopLevelDecls()) {
-      callback(cast<ExtensionDecl>(extension));
-    }
-  }
-}
-
 void Decl::forEachAttachedMacro(MacroRole role,
                                 MacroCallback macroCallback) const {
   for (auto customAttrConst : getSemanticAttrs().getAttributes<CustomAttr>()) {

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1937,11 +1937,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
                           "`" + VD->getBaseName().userFacingName().str() + "`");
       }
     }
-
-    // Visit macro-generated extensions.
-    decl->forEachExpandedExtension([&](ExtensionDecl *extension) {
-      DeclVisitor<DeclChecker>::visit(extension);
-    });
   }
 
 

lib/Sema/TypeChecker.cpp

@@ -297,6 +297,16 @@ TypeCheckSourceFileRequest::evaluate(Evaluator &eval, SourceFile *SF) const {
       }
     }
 
+    // Type-check macro-generated extensions.
+    if (auto *synthesizedSF = SF->getSynthesizedFile()) {
+      for (auto *decl : synthesizedSF->getTopLevelDecls()) {
+        if (!decl->isImplicit()) {
+          assert(isa<ExtensionDecl>(decl));
+          TypeChecker::typeCheckDecl(decl);
+        }
+      }
+    }
+
     typeCheckDelayedFunctions(*SF);
   }